1. Field of the Invention
This invention relates to a method of manufacturing InSb, a compound semiconductor. It particularly relates to a method of manufacturing an InSb device that employs an anodic oxide layer as a structural element.
2. Prior Art Statement
Various methods have been proposed for fabricating semiconductor oxides, which play an important role in semiconductor devices. Because anodic oxides of InSb can be formed at room temperature and exhibit good interface characteristics with InSb, anodic oxide layers play a major role. Because of this, it is essential that anodic oxidation conditions for InSb devices be established.
The InSb anodization process method utilizes the phenomenon of oxidation on the InSb surface by passing a current through an InSb anode immersed in an electrolytic solution or in plasma to form a surface oxide layer. An InSb anodic oxide layer is an excellent electrical insulator, but the anodization conditions may be such as to adversely affect the properties of the interface between the oxide layer and the InSb, or the InSb itself. The constant current process is a widely-used method. The thickness of the anodic oxide layer is controlled by the anodization time under a constant current. However, with this method it is difficult to achieve precise control for a uniform layer thickness over the entire surface. When anodization is performed under a constant voltage, as the oxidation proceeds there is a decrease in the anodization current. When the layer thickness reaches a predetermined value as set in accordance with voltage, the anodization current ceases to flow and the oxidation process comes to a stop. Thus, it becomes possible to control the thickness of the oxide layer by means of the anodization voltage. Hence, by carrying out the anodization for a sufficiently long period for the current to stop flowing, it becomes possible to control the thickness of the oxide layer with precision.
It has however been found that when anodization is conducted for such an extended period, the InSb becomes impregnated with unnecessary impurities that degrade the performance of the InSb device. This has been a problem requiring a solution.